Need help... leaves not looking so hot

This is my first time trying to grow hydroponically and everything looks ok except about half of the plants have brown dead spots on the fan leaves and some are curling down and turning yellow:( I'm not sure what the problem is... I guessed it was an mg deficiency so I just bought some calmag plus. I then flushed each plant with a lot of pH 5.5 R/O water and made a new batch of nutrients and I'm hoping it will cure the problem... but I'm still not sure what the matter is? I was also wondering if I should just cut off the leaves that are curling down and turning yellow. Any input will be greatly appreciated :)

what kind of nutes? Lighting? room temps? humidity? ppms? Age of plants? etc etc etc :)

http://boards.cannabis.com/hydroponi...have-look.html
Here is a link to my grow thread :)

Thank you Weedhound for your response :) It's been about 4 or 5 days since I started to notice the problem and it is steadily getting worse. The good news is it's only affecting 3 out of the 14 plants that I have but I still want to save them if I can. Update on their status is pH 5.75, ppm 475 and res. temp 72 at day 28... temp in room is 77 and 42% humidity. I've been reading like crazy to try to find out what's wrong... what I've come up with is either nute burn or pH problems (most similar looking pictures to mine) but still not sure... I'm going to flush them again with pHed water and turnoff pump to see if their condition improves or not. Thank you for your time and here are some new pics.

classic fert burn

I'm not seeing classic nute burn symptoms- classic would be tip-burn, but this looks to me more like a fungal problem. Or possibly Ca def but I'm leaning towards fungus.

Hey everyone,
Thank you for the responses... Ok so what I'm doing now is continuing to flush the plants to cure the possible fert burn and I've got a fungicide that I might use if it's a fungus. I was just wondering how easy it is to get a fungus. I have a fan blowing on them 24/7 and venting out the old air into the attic. The temp never gets above 82 and humidity at 45%...and that's when I have to close the door. Is there any tell tale signs that it is a fungus? Thank you all for your time:)

Your water temps are slightly warm...that can encourage fungus probs as Stinky mentioned. Ppms of 475 certainly don't seem too high to me....if anything too low.....I'll check your grow log but would like to know what your ratios are with the cal mag etc.......info may be in your log.

I'd stop flushing things...if anything you are low on something....
how old are these plants and what kind are they?
how much cal mag are you using?

Hey Weedhound,
Ok ill stop flushing and put the pump back on the timer... I flushed three times with each time consisting of one gallon phed to 5.8...My reservoir had 12 gallons of R/O water so I looked at the firefox hydro feeding schedule and it said to mix 2 tsp/gal of grow big and 1tbl/gal of big bloom so I did the math out and got 120 ml of GB and 180ml of BB. Then I didn't want to do full strength so I did half... as for the calmag it said to use 5-10ml/gal so I use 5 and got 60ml for the 12 gallons (halved that too). So after the flushing of the three extra gallons it is at 15 now and the ppm is 420, ec is 835, pH is 5.75 and temp is 68. These plants are now 28 days old since the sprout broke through the rockwool and im not sure what kind it is... I got the seeds from a friend who grows outdoors (could that be the problem?). They are asleep right now but they still look good... they are still growing larger every day, like its growing away from the problem area. Ill post some pics tomorrow :) Later